Purpose: Self-regulation is defined as strategic, metacognitive behavior, motivation and cognition aimed at a goal (Zimmmerman and Schunk, 2011). Co-regulation, arguably more aligned with norms in communal cultures, is the process of learners sharing "a common problem-solving plane" through which self-regulatory strategies are learned (Hadwin and Oshaige, 2011, p.247). This paper aims to investigate the impact of co-regulation on self-regulation and math achievement for culturally diverse students. Design/methodology/approach: This empirical study used structural equation modeling framework to estimate the effects of co-regulation on self-regulation and math achievement, as measured by the statewide-standardized test. Surveys measuring students' use of co-regulatory and self-regulatory strategies and standardized math test scores were collected from 625 seventh- and eighth-grade students in a suburban district outside a southeastern urban center in the 2011-2012 academic year. Findings: Results indicated that co-regulation is positively and significantly related to self-regulation strategy use among students in the sample. Self-regulation and co-regulation were positively related to math achievement. Data suggest the modeled relationship of co-regulation, self-regulation and achievement may vary by ethnic group. Originality/value: A large body of literature documents the impact of self-regulation on student achievement, although there is less focus on students of color. This work expands that body of literature by examining co-regulation as a predictor of self-regulation and its mediated effects on student achievement for students of color.